Molecular Details of the Fast Dynamics and Fragility in Polymers

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Technical Summary:Molecular motions define many unique macroscopic properties of polymers, and understanding fundamentals of polymer dynamics is crucial for design of advanced polymeric or composite materials with desired properties. Among various aspects of polymer dynamics, the fast dynamics, i.e. the dynamics in the GHz-THz frequency range, deserves particular attention due to its importance for applications in advanced information and communication technologies, in microelectronics and photonics. Understanding the microscopic mechanisms of the fast dynamics and the temperature variation of segmental relaxation (fragility) in polymeric systems are the main objectives of the proposed research program. A number of experimental techniques (light, neutron and X-ray scattering and dielectric spectroscopy) employed in this program provide detailed microscopic information on the fast and segmental dynamics in polymers, their dependence on molecular structure of the chain. The proposed high-pressure measurements provide a means to separate the role of molecular packing, temperature and monomer structure in the polymer dynamics and the glass transition. Tight collaboration with theory brings deeper understanding and interpretation of experimental results as well as formulation of new ideas. The results will have significant impact on polymer science, and in broader aspect on dynamics of complex systems, materials science and physics in general, and also on biophysics through a better understanding of dynamics of biological macromolecules.Non-Technical Summary:Information and communication technologies are moving to higher frequency and their progress depends strongly on our understanding of materials behavior at this frequency range. The proposed research focuses on fast molecular motions and their role in macroscopic properties of polymeric materials. Advances in the proposed directions will impact various fields of materials science, physics and biophysics. Moreover, understanding the fast dynamics has significant impact on design and synthesis of materials for current and future communication, information and computation technologies, on developments of materials for photonic and microelectronic applications, and on progress in some bio-technologies. The proposed program promotes active international collaboration and collaboration with national multi-user facilities at NIST and ANL. The proposed program also significantly impacts education of future specialists through active involvement of graduate and undergraduate students in this research, developments of graduate courses. Attention is also paid to work with underrepresented groups and K-12 students outreach.